COLUMBUS, Ohio (AP) — A union asked Ohio and federal labor officials on Wednesday to investigate whether a company violated federal wage and hour laws when it shuttered its coal mine to host a campaign event for Republican presidential nominee Mitt Romney.

Murray Energy Corp. said it closed its mine in eastern Ohio for one shift during the Aug. 14 event to ensure the site's security. Coal workers were not paid while the Century Mine in Beallsville was closed.

A Secret Service spokesman on Wednesday said it did not request the mine's closure during Romney's visit.

Service Employees International Union, District 1199, has taken issue comments the company's chief financial officer made to a West Virginia radio station following the campaign event.

Robert Moore, who also is the company's executive vice president, told WWVA in a recent interview that managers "communicated to our workforce that the attendance at the Romney event was mandatory but no one was forced to attend the event."

The station asked Moore why the company didn't pay the coal workers.

"As a private employer, it was our decision," Moore said. "And we made the decision not to pay the people for the day."

Moore said repeatedly in the interview that workers weren't required to go to the political rally, which the Pepper Pike-based company emphasized in a written statement on Wednesday.

"All participation was, and always has been, completely voluntary," the statement said. "Additionally, we do not pay employees who voluntarily attend political events."

The company did not respond to email requests seeking additional information, including the number of employees affected by the closure and the hours the mine was closed.